Driving means for rotary heat exchangers



J. G. LANNING 3,363,478 I DRIVING MEANS FOR ROTARY HEAT EXCHANGERS Jan. 16, 1968 5 Sheets-Shet-l Filed Aug. 19, 1964 Fig. 3

ENTOR INV John 6.

BY h Welded/r D 1 Lanping AGENT J. G. LANNING DRIVING MEANS FOR ROTARY HEAT EXCHANGERS Jan. 16, 1968 Filed Aug. '19. 1964 5 Sheets-Sheet 2 ENTOR. Lanning INV John 6.

AGENT Jan. 16, 1968 J G. ANMNG 3,363,478

DRIVING MEANS FOR ROTARY HEAT EXCHANGERS Filed Aug. 19, 1964 3 Sheets-Sheet 5 I INVENTOR WMDIFM AGENT John G.Lann1'ng United States Patent York Filed Aug. 19, 1964, Ser. No. 390,636 11 Claims. (Cl. 74446) This invention relates to means for driving rotary heat exchangers and more particularly to means for driving such heat exchangers formed of materials having low thermal coefficients of expansion.

It has recently been discovered that certain low-expansion ceramic materials, such as the materials disclosed in United States Patent 3,112,184, issued to R. Z. Hollenbach, function as particularly satisfactory matrix materials for regenerative heat exchangers. Such materials exhibit the advantages of high surface area, high maximum operating temperatures, low thermal conductivities and relatively high specific heats. Rotation of such heat exchangers in the past has been effected by means such as gear teeth cut in the heat exchanger rims. Inasmuch as it is diflicult and expensive to cut gear teeth in ceramics, methods have been sought for sealing metallic ring gears directly to the ceramic rims of the heat exchangers. Due to the fact that those ceramic materials most suitable for the construction of heat exchangers have very low thermal expansions, it has been difiicult to seal relatively high-expansion metal rims to the ceramic rims of the heat exchangers so as to render the seals effective at the high temperatures under which such heat exchangers are required to operate. The only previously feasible technique for effecting such seals has involved heating a metallic band, encircling the ceramic rim with the band and subsequently cooling the band to cause it to contract and tightly grip the ceramic rim. In order to prevent loosening of the band when the heat exchanger is again heated to its operating temperature, it has been necessary to apply the 'band at temperatures higher than the operating temperature of the heat exchanger. The disparity between such high temperatures and room temperatures has resulted in extremely high stresses during periods when the heat exchanger is not in operation. Such stresses are conducive to mechanical failure of the ceramic material.

Accordingly, it is an object of the present invention to provide means for coupling a high-expansion metallic driving means to a low-expansion cylindrical ceramic heat exchanger This and other objects, which will be apparent from the detailed description of the invention, are accomplished by the use of a sinuatcd spring band in engagement with the outer surface of such heat exchanger rim.

The invention will be described with reference to the accompanying drawing, in which:

FIGURE 1 is an elevational view of a radial-flow rotary heat exchanger illustrating one embodiment of the driving means of the invention,

FIGURE 2 is a sectional view taken on line 22 of FIGURE 1,

FIGURE 3 is an isometric view of a portion of the heat exchanger of FIGURES 1 and 2,

FIGURE 4 is an elevational view of a heat exchanger including an alternate form of driving means,

FIGURE 5 is a sectional view taken on line 5-5 of FIGURE 4,

FIGURE 6 is a perspective view of an axial flow heat exchanger including driving means similar to that illustrated in FIGURES 1 and 2,

FIGURE 7 is a sectional view taken on line 77 of FIGURE 6, and

FIGURE 8 is a view similar to that of FIGURE 1, illustrating a modified driving means.

In FIGURES l-3, there is illustrated a radial-flow type rotating regenerative heat exchanger, designated by numeral 10. The heat exchanger comprises two rims 11 and 12 having outer surfaces in the form of circular cylinders and comprising a low-expansion ceramic material, such as that disclosed in United States Patent 2,920,971, issued to S. D. Stookey. Supported by rims 11 and 12 are a plurality of blocks 13 of honeycomb ceramic material of the type disclosed in the above-mentioned Hollenbach patent. The heat exchanger is appropriately supported, by means not shown, so as to permit it to be rotated about an axis designated by numeral 25 by driving gear 14 illustrated in FIGURE 1. The construction and operation of such heat exchangers is described in detail in copending United States application Ser. No. 164,572, filed on Jan. 5, 1962.

Since heat exchanger 10 is designed for operation at very high temperatures, and since the materials comprising rims 11 and 12 and ceramic honeycomb blocks 13 have thermal expansions of substantially zero, the coupling of such a heat exchanger to a metal ring gear, such as gear 16, which gear has a relatively high thermal expansion, cannot easily be effected by a rigid mechanical linkage. Accordingly, the present invention provides, in one embodiment, a linkage comprising at least one metallic sinuated spring band segment 15. Segments 15 comprise a high-temperature spring material, such as Inconel X, an alloy comprising by weight: 72.85% Ni, 14.98% Cr, 6.77% Fe, 2.54% Ti, 1.12% Cb-l-Ta, 0.72% Al, 0.57% Mn, 0.29% Si, 0.08% Cu, 0.05% C and 0.007% S.

Spring band segments 15 are tightly compressed between ceramic rim 12 and ring gear 16. Segments 15 are in transverse compression, that is, they are maintained in compression in a direction transverse to the direction of motion of gear 16, or in a radial direction with respect to axis 25. Due to such compression, frictional engagement is effected between the spring segments and both rim 12 and the inner surface 30 of gear 16. Due to the transverse compressibility of the spring segments, as temperature variations cause variations in the radial distance between the inner surface of ring gear 16 and the outer surface of rim 12, the spring will compress or expand transversely. Thus, stresses in the heat exchanger components will :be minimized, and the ring gear will he maintained in driving relationship to the heat exchanger.

The ring driving means of the embodiment of the invention illustrated in FIGURES 1-3 is formed of at least one segment, rather than as a continuous closed curve about rim 12, in order to permit longitudinal expansion and compression thereof in response to transverse compression and expansion thereof, respectively. Frictional engagement between the spring segments and the respective surfaces is effected by line contact between the surfaces and the crests and troughs of the respective sinuations of the spring. Thus, rotation of driving gear 14, which effects rotation of driven gear 16, will be transmitted by means of spring segments to heat exchanger rim 12. Space is left at the end of a segment in order to permit expansion thereof. The driving means may com prise a single segment having a plurality of sinuations and extending along substantially the entire circumference of rim 12, except for a space between its ends suflicient to permit extension; however, preferably, the driving means comprises a plurality of segments spaced in end-toend relation along the rim and each comprising one or more sinuations.

In order to increase the efiiciency of the coupling be tween gear 16 and rim 12, the configuration of spring segments 15 may be varied from the generally sinusoidal shape illustrated in FIGURES 1-3 to the slanted configuration illustrated in FIGURE 8. According to such variation, each outwardly convex sinuation of the spring is tilted or skewed outwardly in the same direction as the direction of rotation of the heat exchanger. Increased gripping is thereby effected between surfaces otherwise having coefficients of friction low enough to permit slipping. Other means, such as axial grooves or corrugations in the inner surface 30 of gear 16 or on the outer surface of rim 12 may be utilized to increase the efiiciency of the coupling effected by means of a spring band segment.

As described above, the illustrated embodiment of the invention has been utilized in conjunction with a radialfiow type heat exchanger. In such embodiment it is necessary to place the driving spring band at a location whic permits radial flow of gases through the cylindrical periphery of the heat exchanger. When the invention is to be utilized in conjunction with an axial-flow type heat exchanger, the spring band segments may be located as illustrated in FIGURES 6 and 7. Driving band segment 17 is interposed between ring gear 18 and heat exchanger rim 19. Each band segment 17 may comprise one or more sinuations, and any number of segments compatible with the circumference of the heat exchanger rim may be utilized, as long as sufiicient space is maintained there between to permit longitudinal expansion of the segments.

An alternate embodiment of the invention is illustrated in FIGURES 4 and 5. In this embodiment a continuous sinuated spring band 20 is maintained in longitudinal tension about heat exchanger rim 21, which is in the form of a circular cylinder about axis 26. This tension is maintained at a degree sufficient to permit the rim to be driven by the band. Driving gear 22 has teeth which intermesh directly with the indentations in spring band 20. Thus, the spring band simultaneously serves as a driven ring gear and means for frictionally engaging the heat exchanger rim. Since rim 21 has a thermal expansion of substantially zero, changes in temperature will have substantially no effect upon the distances between the respective crests of spring band 20, and expansion and contraction of the band will be accommodated by increase and decrease in the amplitude of the individual sinuations. Inasmuch as rotary heat exchangers are mounted so as to be rotatable with a minimum of friction, it is not necessary that the teeth of driving gear 22 mesh in precise relation with the indentation in spring band 20. Variations in the pitch circle of the gears will have no significant effect upon operation of the heat exchanger. Since the teeth of the driving gear need not extend to the bottoms of the indentations in the spring band, thermal expansion of the driving gear will not subject the ceramic heat exchanger to stress.

It will be appreciated that various materials may be utilized for forming either spring band segments and 17 or continuous spring band 20, depending upon the mass of the heat exchanger and the amount of retarding friction to which the heat exchanger is subjected in its operational environment.

Assembly of the driving means illustrated in FIGURES 1-3 is accomplished by placing ring gear 16 about rim 12 and subsequently partially flattening the spring band segments 15 and inserting them between the ring gear and the rim. The resiliency of the spring material causes the spring band segments to expand transversely and to lock the components into frictional engagement. In the embodiment of the invention illustrated in FIGURES 4 and 5, the continuous ring is expanded to place it in tension and subsequently placed around rim 21 and released, thereby permitting the spring to tighten over the rim. The spring is designed to remain in tension and tightly to grip rim 21 after it has been placed thereover. If desirable, the respective sinuations of continuous spring 20 may be slanted outwardly in the same direction as the direction of rotation of the heat exchanger, in a manner similar to that illustrated with respect to spring segments 15 in FIGURE 8, or rim 21 may be provided with axial grooves or other means for increasing the efficiency of the coupling between the spring band and the rim.

In the appended claims, when the spring bands of the invention are referred to as cylindrical, it is to be understood that the term is used in its mathematical sense and is not to be limited to circular cylinders or cylinders having parallel bases. When the sinuations or indentations of the bands are referred to as axial sinuations, it is meant that the straight lines which form elements of the sinuations are parallel to the axis of the cylinder.

The above-described embodiments of the present invention have been provided solely as illustrations and are intended to be by way of example rather than as limitations of the invention. Accordingly, it is intended that the scope of the invention be limited only by the scope of the appended claims.

I claim:

1. Means for rotating about an axis a heat exchanger having a ceramic rim with a surface in the form of a circular cylinder having said axis as its center, said means comprising a spring having at least one sinuation, said spring being compressible in a radial direction and having an inner surface engaging said surface of said rim in driving relationship thereto, and means for engaging the outer surface of said spring to drive said spring in a generally circular path about said axis.

2. Means for rotating about an axis a heat exchanger having a ceramic rim with a surface in the form of a circular cylinder having said axis as its center, said means comprising a ring gear having an inner surface in the form of a circular cylinder concentric with said cylindrical surface of said rim and separated from said surface of said rim by an annular space, within said space at least one spring band segment having at least one sinuation permitting compression of said spring in a radial direction with respect to said axis, said segment being compressed between and engaging said inner surface of said ring gear and said surface of said rim, and means for rotating said ring gear about said axis.

3. Means for rotating about an axis a heat exchanger having a ceramic rim with a surface in the form of a circular cylinder having said axis as its center, said means comprising a ring gear having an inner surface in the form of a circular cylinder concentric with said cylindrical rim surface and separated from said rim surface by an annular space, within said space a plurality of spring band segments spaced apart from one another in endto-end relationship, each said segment having at least one sinuation permitting compression of said spring in a radial direction with respect to said axis, said segments being compressed between and engaging said inner surface of said ring gear and said rim surface, and means for rotating said ring gear about said axis.

4. Means for rotating about an axis a heat exchanger having a ceramic rim with a surface in the form of a circular cylinder having said axis as its center, said means comprising a ring gear concentric with said cylindrical rim surface and having an inner surface separated from said rim surface by an annular space, within said space at least one spring band segment comprising a plurality of sinuations permitting compression of said spring in a radial direction with respect to said axis, said segment being compressed between and engaging said inner surface of said ring gear and said rim surface, and means for rotating said ring gear about said axis.

5. Means for rotating about an axis a heat exchanger having a ceramic rim with a surface in the form of a circular cylinder having said axis as its center, said means comprising a ring gear concentric with said cylindrical rim surface and having an inner surface separated from said rim surface by an annular space, within said space at least one spring band segment having at least one sinuation, said spring band segment being compressible in a radial direction with respect to said axis, said segment being compressed between and engaging said inner surface of said ring gear and said rim surface solely by friction, and means for rotating said ring gear about said axis.

6. Means according to claim 5 in which each said sinuation slopes outwardly in the same direction as the direction of rotation of said rim.

7. Means for rotating about an axis a heat exchanger having a ceramic rim with a surface in the general form of a cylinder having said axis as its center, said means comprising a continuous sinuated spring band in tension about said rim surface, said band having a plurality of indentations forming a sinuated path about said rim surface, said indentations engaging said rim surface, and a driving gear in intermeshing relationship with said indentations in said band.

8. Means for rotating about an axis a heat exchanger having a ceramic rim with a surface in the form of a circular cylinder having said axis as its center, said means comprising a continuous sinuated spring band in tension about said rim surface, said band having a plurality of indentations forming a sinuated path about said rim surface, said indentations frictionally engaging said rim surface, and a driving gear in intermeshing relationship with said indentations in said band.

9. A heat exchanger comprising a ceramic body rotatable about an axis and having a plurality of passages therein extending radially with respect to said axis between opposed generally cylindrical inner and outer surfaces of said body, a ceramic rim having a coefiicient of thermal'expansion substantially the same as that of said ceramic body at least partially located along an edge of said ceramic body intermediate said inner and outer surfaces, said ceramic rim having an outer surface in the form of a circular cylinder having said axis as its center, a ring gear having an inner surface in the form of a circular cylinder having said axis as its center, said inner surface of said ring gear being separated from said outer surface of said rim by an annular space, within said annular space at least one spring segment compressed between said inner surface of said ring gear and said outer surface of said rim, and means for rotating said ring gear about said axis.

10. A heat exchanger according to claim 9 which includes a plurality of said spring segments within said annular space.

11. A heat exchanger according to claim 10 in which each said spring segment comprises a plurality of sinuations.

References Cited UNITED STATES PATENTS 1,165,772 12/1915 Garrand 64-30 1,424,267 8/1922 Tupper 74-446 1,435,141 11/1922 Serrell 6-4-15 2,103,781 12/1937 Hanson 64-30 2,845,150 7/1958 Stephenson 192-451 X 2,893,224 7/1959 Schmitter 64-15 X 3,061,060 10/1962 Stephenson 192-41 3,177,735 4/1965 Chute 74-448 X 3,228,210 1/1966 Farmer 64-30 3,311,204 3/1967 Barnard 7-4-446 FOREIGN PATENTS 146,527 8/1954 Sweden. 916,370 8/1954 Germany.

MILTON KAUFMAN, Primary Examiner.

DAVID J. W ILLIAMOWSKY, C. I. HUSAR,

Examiners. 

1. MEANS FOR ROTATING ABOUT AN AXIS A HEAT EXCHANGER HAVING A CERAMIC RIM WITH A SURFACE IN THE FORM OF A CIRCULAR CYLINDER HAVING SAID AXIS AS ITS CENTER, SAID MEANS COMPRISING A SPRING HAVING AT LEAST ONE SINUATION, SAID SPRING BEING COMPRESSIBLE IN A RADIAL DIRECTION AND HAVING AN INNER SURFACE ENGAGING SAID SURFACE OF SAID RIM IN DRIVING RELATIONSHIP THERETO, AND MEANS FOR ENGAGING THE OUTER SURFACE OF SAID SPRING TO DRIVE SAID SPRING IN A GENERALLY CIRCULAR PATH ABOUT SAID AXIS. 